U.S. patent number 4,440,492 [Application Number 06/414,713] was granted by the patent office on 1984-04-03 for variable force wide document belt transport system.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Anthony Howard.
United States Patent |
4,440,492 |
Howard |
April 3, 1984 |
Variable force wide document belt transport system
Abstract
A document transport for transporting document sheets over a
copier platen and into a registration position thereon for copying
with a single light reflective, flexible, unapertured and air
impervious wide frictional movable belt providing a uniform light
imaging background for the document sheet, having a selectably
actuatable vacuum system for selectably applying a vacuum to a
vacuum plenum overlying the vacuum belt above the platen, for
lifting all but selected minor areas of the belt away from the
platen and document toward the vacuum plenum when a vacuum is
applied, but and for allowing the belt to drop into planar
engagement with a document sheet on the platen over a much larger
area of said belt when the vacuum is removed, and belt deforming
rollers deforming the selected minor areas of the belt away from
the vacuum plenum towards the platen for selective area driving of
a document sheet on the platen with these deformed minor areas or
protuberances of the belt when the vacuum is applied.
Inventors: |
Howard; Anthony (Rochester,
NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
23642636 |
Appl.
No.: |
06/414,713 |
Filed: |
September 3, 1982 |
Current U.S.
Class: |
355/76; 271/233;
271/275; 271/6 |
Current CPC
Class: |
G03B
27/64 (20130101); G03B 27/625 (20130101) |
Current International
Class: |
G03B
27/64 (20060101); G03B 27/62 (20060101); G03B
027/62 (); G03B 027/64 () |
Field of
Search: |
;355/76,3SH,14SH
;271/6,10,233,275 ;428/494 ;226/97 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"Belt Energized Antiskew Rolls", Victor Castro-Hahn, Xerox
Disclosure Journal, vol. 6, No. 6, Nov./Dec. 1981, p. 345..
|
Primary Examiner: Wintercorn; Richard A.
Claims
What is claimed is:
1. In a document transport for transporting document sheets over a
copier platen and into a registration position thereon for copying
with a single, light reflective, flexible, unapertured and air
impervious wide frictional movable belt providing a uniform light
imaging background for the document sheet, the improvement
comprising:
selectably actuatable vacuum means for selectably applying a vacuum
to vacuum plenum means overlying said vacuum belt above said
platen,
said vacuum means lifting all but selected minor areas of said belt
away from said platen toward said vacuum plenum means when a vacuum
is applied to said vacuum plenum means,
said vacuum plenum means allowing said belt to drop from said
vacuum plenum means into engagement with a document sheet on the
platen over a much larger area of said belt when said vacuum is
removed from said vacuum plenum means as compared to when said
vacuum is applied to said vacuum plenum means, and
belt deforming means for deforming said minor areas of said belt
away from said vacuum plenum means towards said platen for
selective area driving of a document sheet on the platen with said
deformed minor areas of said belt when said vacuum is applied to
said vacuum plenum means.
2. The document transport of claim 1 wherein said belt deforming
means comprises rollers deformably engaging said selected minor
areas of said belt for deforming said belt into driving engagement
with a document sheet being transported across said platen while
other areas of said belt are lifted out of engagement with the
document sheet by said vacuum applied to said vacuum plenum
means.
3. The document transport of claims 1 or 2 wherein said vacuum
plenum means and said belt are adapted to allow said belt to
non-deformably planarly overly and engage a document sheet when
said vacuum is removed from said vacuum plenum means.
4. The document transport of claims 1 or 2 wherein said belt is
lifted away from said platen by approximately 0.25 to 1 millimeter
except in said selected minor areas when said vacuum is applied to
said vacuum plenum means.
5. The document transport of claims 1 or 2 wherein said belt is an
endless loop with upper and lower flights and said vacuum plenum
means comprises a fixed generally planar vacuum surface member
mounted inside said endless loop and overlying said second
flight.
6. The document transport of claims 1 or 2 wherein said vacuum
plenum means is apertured for said belt deforming means and said
belt deforming means extend through said apertures.
7. The document transport of claims 1 or 2 further including
pressure roller means engaging the belt in said registration
position.
8. The document transport of claim 5 wherein said vacuum plenum
means has separate portions to which vacuum may be selectively
applied.
9. The document transport of claims 1 or 2 further including means
for selectively applying a positive pneumatic pressure instead of a
vacuum to said vacuum plenum means.
10. A method for transporting a document sheet over a copier platen
with a single wide unapertured frictional belt providing a uniform
light imaging background for the document sheet comprising the
steps of:
applying a vacuum lifting force over a substantial area of the back
of said belt over said platen to deform said belt into a generally
planar surface spaced from the document sheet with at least two
belt protuberances extending towards said platen in selected minor
areas of said belt,
engaging and transporting the document sheet over the platen with
said deformation proturbances of said belt, and then
removing said vacuum to remove said deformation of said belt and
allowing said belt to substantially planarly overly the document
sheet and to greatly increase the area of contact between the belt
and the document sheet.
11. The method of claim 10 wherein said belt is accelerated to
eject the document sheet from the platen with said vacuum removed
and then said vacuum is reapplied to said belt for the feeding of a
subsequent document over the platen.
12. The method of claims 10 or 11 wherein said deformation
proturbances are formed in said belt by applying mechanical
pressure to the back of the belt in said selected minor areas with
sufficient pressure to overcome said vacuum lifting force in said
selected minor areas.
13. The method of claims 10 or 11 wherein said vacuum lifting force
is selectively applied to only substantially all of the upstream
half of belt area overlying the platen or to substantially the
entire belt area overlying the platen.
14. The method of claims 10 or 11 including the further step of
applying a pneumatic pressure to said belt.
Description
The present invention relates to a document handling system and
more particularly relates to an improved method and apparatus for
automatically transporting, registering and deskewing individual
document sheets to be copied on a copier platen with a wide
unapertured transport belt having a variable vacuum controlled
normal force.
As xerographic and other copiers increase in speed, and become more
automatic, it is increasingly important to provide higher speed yet
more reliable and more automatic handling of the original document
sheets being copied, i.e. the input to the copier. It is desirable
to feed, register and copy document sheets of a variety or mixture
of sizes, types, weights, materials, conditions and susceptibility
to damage, yet with minimal document jamming, wear or damage by the
document transporting and registration apparatus, even if the same
documents are automatically fed and registered repeatedly, as for
recirculating document precollation copying.
Even with slower copying rate copiers, it has become increasingly
desirable to provide at least semi-automatic document handling,
allowing an operator to "stream feed" originals into an input of
the copier document handler, with the document handler doing the
deskewing, final registration and feeding of the documents into and
through the copying position, and then ejecting the documents
automatically. However, for compact and low cost copiers, an
appropriate document handler must also be simple, low cost and
compact.
A preferable document handling system is one that uilizes an
existing or generally conventional copier optical imaging system,
including the external transparent copying window (known as the
platen) of the copier. It is also desirable that the document
handling system be readily removable, as by pivoting away, to
alternatively allow the copier operator to conventionally, manually
place documents, including books, on the same copying platen. Thus,
a lighter weight document handler is desirable. It is also
desirable for the same registration edge or position to be
available for such manual copying as is used for the document
handler.
In the description herein the term "document" or "sheet" refers to
a conventional flimsy sheet of paper, plastic, or other
conventional or typical individual image substrate (original or
previous copy), and the like, and not to microfilm or electronic
image originals, which are generally much easier to manipulate.
However, the terms "copier" or "copying" here are intended to
encompass electronic document reading devices which record or
transmit the information read from the document in electronic or
other form not limited to copy sheets.
Although faster and more accurate automatic registration of the
individual original document sheets at the correct position on the
platen to be copied is desired, it is difficult to accomplish
without skewing (slightly rotating) the document and/or damaging
the edge of the document being stopped. Document sheets can vary
widely in sheet size, weight, thickness, material, condition,
humidity, age, etc.. Documents may have curls, wrinkles, tears,
"dog-ears", cut-outs, overlays, paste-ups, tape, staples, adhesive
areas, or other irregularities. Unlike copy sheets, which generally
are all from the same batch and cut from the same paper reams, and
therefore of almost exactly the same condition and size, original
document sheets often vary considerably even if they are all of the
same "standard" size, (e.g. letter size, legal size, A-4, B-4,
etc.) because they have come from different paper batches or have
variably changed size with different age or humidity conditions,
etc.. Yet it is desirable to automatically or semi-automatically
rapidly feed, register and copy a set of individual documents with
a mixture of sizes, types, and conditions without document jams or
document damage and with each document correctly and accurately
aligned to the registration position.
One of the most difficult to achieve requirements for automatic
document handling is the accurate and reliable, but safe,
registration of the original document at the proper position for
copying. Conventionally the document is desirably automatically
either center registered or corner registered (depending on the
copier) by the document handler at a pre-set registration position
relative to the copier platen, with two orthogonal edges of the
document precisely aligned with two registration lines of the
copier platen i.e. with the original document aligned with the
copier optics and copy sheet registration system. This registration
accuracy is desirably consistently within less than 1 millimeter.
If the document is not properly registered, then undesirable dark
borders and/or edge shadow images may appear on the ensuing copy,
or information near an edge of the document may be lost, i.e. not
copied onto the copy sheet. Skewing can also affect proper
restacking of the documents.
As shown in the cited art, document handling systems have been
provided with various document transports to move the original
document sheets over the copier platen and into and out of
registration. Various combinations of such transports are known
with various registration devices or systems. It is known in the
art to register the original document for copying at the
appropriate position relative to the transparent copying window in
various ways. Typically the document sheet is registered by driving
it against a gate or stop at or adjacent one edge of the platen.
This may comprise projecting aligned fingers, or roller nips, or a
single vertical surface, against which an edge of the sheet is
driven into abutment to register the sheet. An important function
of such registration is to also deskew the moving original
document, i.e., to properly rotate and align it with the
registration line as well as to determine and control its
registration position.
As indicated, it is conventional to provide either fixed or
retractable registration finger or gate document stopping edges
aligned along the one edge of the platen, so as to physically
register the document in its copying position. This also reduces
transport criticality, i.e. allows slip or skewing of the document
feeder to be accommodated and corrected. The document transport can
be designed to slip briefly relative to the document lead edge
striking the registration edge stop until positive deskewing and
full registration are achieved. However, the same platen transport
sheet feeder is preferably used to drive a document onto and off of
the platen before and after copying as well as registering the lead
edge of the document at the downstream platen edge. Registering the
trail edge of the document by reversing the feeder and backing the
document into a fixed registration edge at the upstream edge of the
platen may be alternatively provided. In some document handling
systems a system for also side registering or laterally positioning
the document on the platen is used, i.e. positioning of the
original on two axes on the platen. However this is not required,
and lateral registration may be done upstream of the platen.
A severe limitation on such frictional over-platen document sheet
transport and registering systems is that they must have sufficient
drive force to reliably feed the document sheet, but must slip
relative to the platen glass when no document sheet is therebetween
without scratching or wearing the glass such that imaging through
the glass is affected. As indicated above, the document transport
normally needs to also slip relative to the document when the
document is stopped by the registration edge stop. Further, the
overplaten transport should minimize "show around" problems-i.e.
undesirable dark areas or images on the copy sheet, especially for
undersized documents, by visible portions of the transport
extending beyond the document edges during copying. This has led to
the use of single large white elastomeric belts for many document
handlers in lieu of rollers or multiple belts. However such single
belt systems have been found to have some inherent compromises in
feeding and registration reliability. In particular, both the belt
frictional characteristics and its normal force (the pressure of
the belt against the document) are quite critical, and typically
requires regular maintenance and adjustment. This is discussed, for
example, in U.S. Pat. No. 4,353,541 issued Oct. 12, 1982 by William
J. Parzygnat and the art therein, which includes solenoid actuated
"kicker" or normal force belt loading rollers, such as that
disclosed in Vol. 6, No. 6, Nov./Dec. 1981, p. 345 of the "Xerox
Disclosure Journal". Single wide belt document handlers in a
reversible belt trail edge registration system are shown, for
example, in U.S. Pat. Nos. 3,504,908 issued Apr. 3, 1980 to J. R.
Kruger, and 4,076,233 issued Feb. 28, 1978 to C. Knight, et
al..
Examples of the peculiar or special requirements for platen
transport belt material (compared to other belts) are disclosed in
U.S. Pat. No. 4,314,006 issued Feb. 2, 1982 to James A. Lentz and
Joseph H. Moriconi.
A particular such limitation or compromise is that a document
transport system which minimizes the introduction of document sheet
skewing in feeding from the document set stack up to the
registration position on the platen, and in the return therefrom,
is highly desirable, in order to reduce the amount of skew needing
correction (deskewing) in the registration position. Yet it is also
desirable, but normally incompatible, to maximize document skewing
during the document registration, i.e. to allow the document to
rotatably slip relative to the belt to be freely deskewed as it is
driven into alignment with the registration edge. The present
invention compatibly provides both of these features.
To overcome the skewing problem it is known to use an apertured
vacuum belt. However, this creates problems in undesirable imaging
of the belt apertures onto the copies, and/or difficulties in
registering the document on the platen without a servo-driven belt
drive and in providing any slip for deskewing the document. Noted,
for example, are U.S. Pat. Nos. 4,298,277 and 4,286,870 to Morton
Silverberg, 4,043,665 issued Aug. 23, 1977 to J. R. Caldwell, and
Japanese Application Laid Open No. 51-120717 laid open Oct. 22,
1976 (FX/1176).
An air pressure bladder or mechanical clamp to flatten a document
belt and underlying document against a platen during copying is
also known, e.g. U.S. Pat. No. 3,937,454 issued Feb. 10, 1976 (Re.
29,178) by Richard E. Colwill.
The present invention may be utilized as part of a recirculating
document handler as well as for an automatic or semi-automatic
document handler. Some examples of further details of exemplary
recirculating document handlers with on-platen registration
document transport and deskewing for which the present invention
may be substituted are disclosed in U.S. Pat. Nos. 4,335,954
issuing June 22, 1982 to Russell L. Phelps; 4,278,344 issued July
14, 1981 to R. B. Sahay; 4,270,746 issued June 2, 1981 to T. J.
Hamlin and 4,076,408 issued Feb. 28, 1978 to M. G. Reid, et
al..
In technologies or arts other than original document sheet platen
transport and registration systems there are, of course, many other
pneumatic belt or tape control systems per se. Examples include
U.S. Pat. No. 3,087,664 issued Apr. 30, 1963 to D. N. Streeter.
Examples of various other patents teaching document handlers and
also control systems therefor, including document path switches,
are U.S. Pat. Nos.: 4,054,380; 4,062,061; 4,076,408; 4,078,787;
4,099,860; 4,125,325; 4,132,401; 4,144,550; 4,158,500; 4,176,945;
4,179,215; 4,229,101; 4,278,344 and 4,284,270. Simple software
instructions in a copier's conventional microprocessor logic
circuitry of document handler and copier control functions and
logic, as taught by the above and other patents and various
commercial copiers, are well known and preferred. Fixing of such
software in read only memory (ROM) or programmable (PROM) hardware
connected with or as part of the copier controller microprocessor
is preferred. However, it will be appreciated that the document
handling functions and controls described herein may be
alternatively conventionally incorporated into a copier utilizing
any other suitable or known logic circuits, switch controllers,
etc.. Electrical control signals may be used to activate
conventional motors, cams, solenoids, etc.. Software for functions
described herein may vary depending on the particular
microprocessor or microcomputer system utilized, of course, but
will be already available to or readily programmable by those
skilled in the art without experimentation from the descriptions
provided herein.
All references cited herein, and their references, are incorporated
by reference herein for appropriate teachings of additional or
alternative details, features, and/or technical background.
The present invention desirably overcomes or reduces various of the
above-discussed problems. A desirable feature of the document
handling system disclosed herein is to provide a document transport
for a copier platen which automatically provides a lighter driving
force during registration of the original document sheet on the
platen than the driving force on the document when the document is
entering onto the platen, so as to provide reliable feeding yet
reduce the chances of buckling or damaging the document during that
portion of its transport in which it is being registered, thereby
overcoming a tendency of many present document transport belt
systems to provide either too much or too little document driving
force for one or both of these different transport positions and
conditions, yet without requiring a multiple belt or roller system
with attendant show-through or show-around copy defect problems
from imaged belt edge shadows or contamination.
A preferred feature disclosed herein is to provide, in a document
transport for transporting document sheets over a copier platen and
into a registration position thereon for copying with a single
light reflective, flexible, unapertured and air impervious wide
frictional movable belt providing a uniform light imaging
background for the document sheet, the improvement comprising:
selectably actuatable vacuum means for selectably applying a vacuum
to vacuum plenum means overlying said vacuum belt above said
platen, said vacuum means lifting all but selected minor areas of
said belt away from said platen toward said vacuum plenum means
when a vacuum is applied to said vacuum plenum means, said vacuum
plenum means allowing said belt to drop from said vacuum plenum
means into engagement with a document sheet on the platen over a
much larger area of said belt when said vacuum is removed from said
vacuum plenum means as compared to when said vacuum is applied to
said vacuum plenum means, and belt deforming means for deforming
said minor areas of said belt away from said vacuum plenum means
towards said platen for selective area driving of a document sheet
on the platen with said deformed minor areas of said belt when said
vacuum is applied to said vacuum plenum means.
Further features which may be provided by the method and apparatus
disclosed herein, individually or in combination, include those
wherein said belt deforming means comprises rollers deformably
engaging said selected minor areas of said belt for deforming said
belt into driving engagement with a document sheet being
transported across said platen while other areas of said belt are
lifted out of engagement with the document sheet by said vacuum
applied to said vacuum plenum means; wherein said vacuum plenum
means and said belt are adapted to allow said belt to
non-deformably planarly overly and engage a document sheet when
said vacuum is removed from said vacuum plenum means; wherein said
belt is lifted away from said platen by approximately 0.25 to 1
millimeter except in said selected minor areas when said vacuum is
applied to said vacuum plenum means; wherein said belt is an
endless loop with upper and lower flights and said vacuum plenum
means comprises a fixed generally planar vacuum surface member
mounted inside said endless loop and overlying said second flight;
wherein said vacuum plenum means is apertured for said belt
deforming means and said belt deforming means extend through said
apertures; or further including pressure roller means engaging the
belt in said registration position, wherein said vacuum plenum
means has separate portions to which vacuum may be selectively
applied; and further including means for selectively applying a
positive pneumatic pressure instead of a vacuum to said vacuum
plenum means.
Another disclosed feature is a method for transporting a document
sheet over a copier platen with a single wide unapertured
frictional belt providing a uniform light imaging background for
the document sheet comprising the steps of: applying a vacuum
lifting force over a substantial area of the back of said belt over
said platen to deform said belt into a generally planar surface
spaced from the document sheet with at least two belt protuberances
extending towards said platen in selected minor areas of said belt,
engaging and transporting the document sheet over the platen with
said deformation protuberances of said belt, and then removing said
vacuum to remove said deformation of said belt and allowing said
belt to substantially planarly overly the document sheet and to
greatly increase the area of contact between the belt and the
document sheet.
Further disclosed features are wherein said belt is accelerated to
eject the document sheet from the platen with said vacuum removed
and then said vacuum is reapplied to said belt for the feeding of a
subsequent document over the platen and said deformation
protuberances are formed in said belt by applying mechanical
pressure to the back of the belt in said selected minor areas with
sufficient pressure to overcome said vacuum lifting force in said
selected minor areas.
Various of the above-mentioned and further features and advantages
will be apparent from the examples described hereinbelow of
specific apparatus and steps of operation. The invention will be
better understood by reference to the following description of one
specific embodiment thereof including the following drawing figures
(approximately to scale) wherein:
FIG. 1 is a side view of an embodiment of an exemplary document
handling apparatus utilizing the document transport and
registration system of the present invention; and
FIG. 2 is a plan (top) view of the apparatus of FIG. 1.
The exemplary document sheet handling system disclosed in FIGS. 1
and 2 may be conventional except as otherwise described herein, and
may be mounted to any suitable or conventional copier. Disclosed
here as one example, but not limited thereto, is a semi-automatic
document handler (SADH) unit 10. It is conventionally mounted over
a conventional copier platen, preferably pivotably removable for
alternative manual document placement on the platen. Alternatively,
however this document handler 10 may be the platen transport
portion of a recirculating document handler providing precollation
copying. A document sheet 12 may be conventionally fed to the
upstream end or entrance to the document handler 10, either
manually, or automatically fed from a stack of document sheets, as
is known in the art. The document handler 10 receives the document
sheet 12 and is designed to transport it reliably into the platen
registration position for registered imaging thereof by the copier.
Registration here is illustrated by a conventional retractable
registration edge stop 13 at the downstream edge of the copier
platen 14. As previously discussed, the requirements for the
transporting of the document into the platen registration area 15
are different from the desired feeding forces on the document both
prior and subsequent thereto. In the platen registration area 15
the document transport must slip relative to the document sheet 12
to prevent buckling or overdriving of the lead edge of the document
sheet against the fingers or gates of the registration edge stop
13. Also it is desirable to allow the document sheet to skew
slightly during this final movement thereof into registration so as
to allow the transport to align the document to the line of the
registration edge.
This registration skewing and slipping allowance is however, quite
inconsistent with the desired no-skewing upstream feeding of the
document before it reaches the registration area 15. It is also
inconsistent with the desired rapid and non-skewing downstream
ejection of the document from the platen after copying of the
document is completed. That is, after the document has been
registered and illuminated for exposure, it is desirable that the
registration edge stop 13 be lowered out of the document path by a
solenoid or other suitable mechanism and that the same document
transport then be usable, by itself or with limited assistence, to
rapidly eject the document from the downstream edge of the platen
into a suitable catch tray or the like, and also to simultaneously
rapidly feed on the next document to be copied. This ejection
requires rapid acceleration of the document sheet which increases
potential slippage or skew problems, both for the document being
ejected and for the next document being fed in at high speed at the
upstream or input area of the platen.
This belt 16 may be constructed of conventional single wide white
document belt materials, as described above. In fact because of the
system disclosed herein, its frictional characteristics are much
less critical. Further, it is intended not to require the daily
cleaning and lubricating by silicone oiling or a "kyaar" pad or
dusting powder conventionally provided for such belts. The mounting
of the belt may be basically conventional, but with less belt
tension, as will be described. However, with the present system,
there is additionally provided a vacuum plenum or manifold 18. The
lower surface 19 of the vacuum plenum 18 is apertured to apply a
vacuum between the vacuum plenum 18 and the back of the lower
flight of the belt 16. This surface 19 is a planar and preferably
approximately 1 mm above the planar surface of the platen 14.
However, it may be slightly curved away from the platen, i.e. or
spaced by a greater distance, at the document input or upstream
edge of the platen. A vacuum is selectively applied to the vacuum
plenum 18 to lift the belt 16 up against the surface 19. Its vacuum
is applied by conventional small vacuum blower 20 through a valve
system 22 connecting between the blower and the plenum, as will be
further described hereinbelow.
The belt 16 may be conventionally mounted and loosely tensioned
between a downstream roller 24 and an upstream roller 26 overlying
but extending beyond the respective downstream and upstream edges
of the platen 14. The downstream roller 24 may be conventionally
motor driven to provide the belt movement and corresponding
document movement. However, unlike a conventional single belt
system, the tensioning is not critical and is low. That is the belt
is relaxed and under low tension so that in the absence of a vacuum
applied to the vacuum plenum 18, substantially the full weight of
the lower flight of the belt 16 can rest with a corresponding
normal force against the back of the document 12. This is contrary
to the normal mounting in which the belt tension is critical or
sensitive because this belt tension must be utilized to partially
counteract the belt weight to prevent excessive normal force on the
document. Thus, with the present system, the maximum normal force
(with no vacuum applied) is substantially higher, in fact so high
as to substantially prevent document skewing and proper
registration. Nor does the belt require lubricating at regular
intervals after cleaning to reduce its frictional feeding force.
This overcomes the known problem of adhesion between the freshly
cleaned and lubricated belt and the platen which can cause a belt
in effect to "stick" to the platen and have excessive starting
torque especially after a long period of inactivity. With the
present system, the frictional driving force, which is the function
of both of the coefficient of friction and the normal force, is
substantially reduced by the selective application of the vacuum
and therefore the maintenance of a lower coefficient of friction is
not as critical. Furthermore, the vacuum application directly lifts
the belt away from the platen and thereby overcomes the
abovedescribed surface adhesion effect before a startup of the belt
movement by greatly reducing the contact area.
The plenum apertured surface 19, and therefore the area of applied
vacuum, comprises a substantial or major area of the belt surface
overlying the platen. However, an important feature disclosed
herein is that selected minor areas of the belt are not lifted away
from the platen toward the vacuum plenum means even when the vacuum
is applied thereto. This is provided by rollers 28 and 29 within
the area of the vacuum plenum 18 but extending through apertures or
wheel wells 30 therein. These small rollers provide actual
deformations or protuberances of the flexible and resilient belt 16
at fixed positions overlying the platen, even though the belt
itself is moving past these rollers 28 and 29 during its document
feeding operation. These belt protuberances engage and transport
the document sheet and provide the frictional drive to the document
sheet in a selective manner.
Specifically there is disclosed here a single small downstream
roller 28 in the platen registration area 15. It is slightly spaced
from the registration edge stop 13 in a position to engage a
standard document sheet 12 being driven into registration centrally
thereof in the transverse dimension of that document. The rollers
29 are a transversely spaced pair of rollers overlying the upstream
or input area of the platen. They provide two transversely spaced
areas of belt contact with a document being fed onto the platen for
positively feeding the document with two small areas of high normal
force sufficiently transversely spaced apart to prevent skewing of
the document relative to the belt. These rollers 29 are spaced
sufficiently far upstream so that a normal sized document is
released from the nips under these upstream rollers 29 before the
lead edge of the document reaches registration against the edge
stop 13. Thus for the last (registration and deskewing) portion of
the document movement across the platen, the document is primarily
under the control of only the single central downstream roller 28.
This roller 28 is adapted to allow some rotation of the document
about its nip area deskewing the document as it is driving the
document against the edge stop 13, providing a vacuum is applied
therearound in the vacuum plenum 18 to lift the remainder of the
belt over the document up with sufficient vacuum force to allow
document slippage relative to the rest of the belt.
Once the document sheet has been driven into registration with the
controlled driving and slippage provided by the belt normal force
control provided by the vacuum plenum 18 and the 3 rollers 28 and
29, the forward movement of the belt 16 is stopped and the vacuum
is removed from the vacuum plenum 18 by the valve system 22. In
fact this removal of vacuum may be initiated slightly before
registration is achieved, since a finite time is required for the
belt release. Upon the removal of the vacuum, the full weight of
the belt 16 is applied over the entire belt surface overlying the
document. This provides a flattening or clamping of the document
against the platen to assist in its proper exposure. I.e. to insure
that all of the document is within the depth of field of the copier
optics under the platen, by removing document wrinkles or curls,
etc.. After the document exposure imaging is completed, by any
suitable imaging system, such as a scanning lamp or flash
illumination, the document is then ejected automatically from the
platen for the copying of the next document sheet. For this
document ejection the vacuum is not reapplied. That is, the full
normal force weight of the belt is maintained on the document sheet
to assist in the ejection of the document by increasing the total
feeding force and also greatly increasing the area of contact
between the belt and the document sheet, as compared to the input
feeding cycle in which the vacuum was applied. This also prevents
skewing on ejection and thus aids in restacking. As the belt is
accelerated to eject the document sheet from the platen the vacuum
is then automatically reapplied to the belt for the feeding of a
subsequent document sheet over the platen. This relifting of the
belt at the input area also provides a gap between the belt and the
platen there which assists in the insertion of the document sheet
as well as reestablishing the two discrete input feeding areas
under the two upstream rollers 29.
Referring further to the rollers 28 and 29, they are provided with
either gravity loading from their weight or the weights of their
mounting components and/or a downward spring loading. This provides
sufficient force so that a vacuum applied to the plenum apertured
surface 19 to the rest of the belt surface will not lift the belt
in the areas under these rollers. That is, the downward normal
force of these rollers is sufficient for their area to counteract
the vacuum force and deform the belt in their area and maintain a
nip between each roller and the platen surface. The axes or
mounting shafts of the rollers may be loosely mounted in vertical
slots to effectively allow the rollers to float vertically with
respect to the rest of the platen cover unit and therefore
eliminate any criticality of alignment with the platen or any
criticality of the positioning of the rollers 24 and 26 relative to
the platen.
The document handler 10 and its transport system provides the
advantages of an unapertured wide belt transport system without
many of its disadvantages. That is, the belt 16 provides a
completely uniform light reflective background for the document
imaging which has no show-through or show-around problems. Yet a
variable force and selectively controlled transport and
registration system is provided in which both the applied areas of
the belt and the applied normal force are selectively controlled
for providing both non-slip feeding of the document during
infeeding and ejection, yet providing the desired slip conditions
between the belt and the document as the document is being
registered. When the vacuum is applied, the document feeding is
under the control of the small minor areas of the belt underlying
the rollers 29 or the roller 28, depending on the document
position. The rest of the belt is lifted either partially or
entirely out of contact with the document and the platen. This also
results in a lower friction between the moving belt and the platen.
Furthermore the friction between the moving document and the platen
is also reduced. The document may effectively "float" in the air
gap between the belt and the platen as it is driven across the
platen by the roller nip contacts of rollers 29, and then of roller
28, with the primary document normal and driving force being only
that locally applied by these rollers.
The plenum apertured surface 19 against which the belt is pulled by
the applied vacuum may be coated with any suitable solid or other
lubricant material. The back of the belt, which rides against the
surface 19, may likewise be either formed or treated to have a low
friction surface, since neither of the latter two surfaces are
utilized for either document transport or imaging background.
The outer surface of belt 16 overlying the platen, even though it
is a uniform and unapertured surface, actually functions in two
different modes as if it were two different types of document
transport. When the vacuum is applied, the belt in effect acts as
three spaced frictional rollers engaging the document rather than
as a belt. In contrast, when the vacuum is removed, the belt acts
as a heavy, document flattening, high normal force, friction
belt.
Further features may be provided with the present system. The valve
system 22 and its connection to the vacuum plenum 18 may be through
plural, dual mode vacuum/pressure valves V and V', as shown rather
than through a single vacuum cutoff or dump valve. That is, the
vacuum plenum 18 may be divided into two or more separate plenums
to which either vacuum or pressure may be selectively separately
applied. Here this is illustrated by dividing the vacuum plenum 18
into an upstream portion 42 and a downstream portion 44
respectively, connected individually through solenoid controlled
valves V' and V to the vacuum or pressure side outputs of blower
20. Applying pneumatic air pressure instead of a vacuum to the
vacuum plenum 18 is an additional feature which may be provided to
even further increase the belt normal force and its document
flattening effect for document exposure and/or ejection, if
desired. A lip seal may be provided on the plenum surface 19
between the two plenum portions 42 and 44 to assist in simultaneous
respective application of pressure and vacuum as discussed below. A
further feature which may be provided is a conventional vertically
repositionable ejection normal force or kicker roller 40 which may
be pressed into the back of the belt over the registration edge
stop 13 to prevent the document from escaping between the belt 16
and the edge stop 13 during registration, and to assist in document
ejection when the registration edge stop is lowered out of the
document path. The registration edge 13 may be segmented with
spaced fingers to interdigitate with corresponding grooves in the
roll 24 (corrugated to match) for further registration
assurance.
All of these components may of course be conventionally actuated
through the conventional copier controller 100 at the appropriate
times. The separation of the vacuum plenum 18 into separate areas
allows further sophistication of the control system. That is, a
vacuum may be applied over the entire upstream portion of the belt
through the plenum portion 42 for the infeeding of a subsequent
document at the same time as the vacuum is removed (or a pressure
applied) to the downstream plenum portion 44 for ejection of the
preceding document simultaneously therewith with maximum normal
force and contact area. This is useful for the sequential stream
feeding of documents to be copied in rapid succession where the
belt 16 is utilized to feed onto the platen a subsequent document
at the same time as it is ejecting the preceding document from the
platen. That is, vacuum may be applied first to only the upstream
half of the belt area and then to the entire belt area and then to
none of the belt area and then again to only the upstream area,
etc..
While not illustrated herein, it will be appreciated that a simple
solenoid or other mechanism may be utilized to provide retraction
at appropriate times of the rollers 28 and/or 29, as desired. This
could be utilized, for example, in a system cited in the above art,
wherein, unlike the system here, the registration edge is fixed and
at the upstream edge of the platen, and the document movement is
reversed by a brief reversal drive of the belt to back the trail
edge of the document sheet into registration. In that type of
system it may be desirable to lift one or both of the rollers 29
briefly during this reverse movement of the belt for assisting
registration slip and maximizing deskewing, in coordination with
the vacuum lifting of the belt during this registration
operation.
It will be appreciated that there are a number of other advantages
provided by the present system in addition to those described
hereinabove. For example, because of the reduced contact areas
during most of the belt movement between the document paper and the
platen glass, as well as between the belt and the platen glass, and
between the belt and the document, wear and contamination and
static electricity generation and adhesion therefrom may be
reduced. The belt thickness may be reduced because of the lower
tension. A simpler mounting arrangement for the rollers 24 and 26
may be provided since the spacing therebetween for belt tensioning
is not critical. The solid fixed vacuum plenum surface 19 provides
a solid surface against which the belt may be pressed for cleaning
the belt when the platen cover unit is lifted. Reduced drive
torque, especially on startup of the system after overnight
shutdown, may be provided. The tolerance of the system to thinner,
lighter weight or more delicate documents may be improved. The belt
surface texture and condition is not as critical, particularly as
to its frictional characteristics. The registration nip roll or
kicker roller 40 is not as critical, and may be retracted or
completely eliminated, yet still allowing light-weight document
handling capability to be improved.
The embodiment disclosed herein, and others, are intended to
provide a more positive and reliable yet gentle and automatic
control of the driving and registration forces on the document
sheet during the entire process of feeding, registering, deskewing,
and ejecting the document. It will also be appreciated that the
embodiment described herein is merely exemplary and that other
variations, modifications, refinements, or alternative embodiments
may be made by those skilled in the art from this teaching. They
are intended to be encompassed by the following claims.
* * * * *